A chip carrier mounting pad or "footprint" may be defined as the metallized artwork leads on an interconnection medium such as a printed circuit board to which a leadless chip carrier may be soldered or otherwise mounted. Traditionally, each size leadless chip carrier, having for example, numbers of pads or terminals ranging from 16 to 128, requires its own custom footprint corresponding precisely to the number and pad configuration. Because of this, interchangeability of leadless chip carriers can only occur if the same size carrier package is used. Thus, a 20 pad carrier cannot be mounted on a 16 lead footprint. This arrangement takes away a certain degree of freedom, particularly in circuit design where changes frequently occur. Additionally, during the "burn in" and test of integrated circuit chips, an interconnection medium must be provided having the full range of custom footprints corresponding to the respective carriers.
It is apparent that what is needed is a universal pad layout or footprint, which will accommodate a wide range of leadless chip carrier sizes. The present invention provides such a layout.